1. Field of the Invention
This invention relates to substituted amides that are useful as inhibitors of CCR10 activity and are thus useful for treating a variety of diseases and disorders that are mediated or sustained through the activity of CCR10 including inflammatory skin diseases, allergic asthma and melanoma. This invention also relates to pharmaceutical compositions comprising these compounds, methods of using these compounds in the treatment of various diseases and disorders, processes for preparing these compounds and intermediates useful in these processes.
2. Brief Description of the Art
Chemokine receptors play an important role in mediating tissue specific recruitment of leukocytes to sites of inflammation. Within the blood there is a subset of memory T cells that preferentially homes to the skin. This subset is defined by expression of the cutaneous lymphocyte antigen (CLA), a lectin, which binds to E-selectin on dermal endothelial cells and promotes trafficking. Although the subset of CLA-expressing cells constitutes only 10-15% of the circulating T cell pool, these cells are found in abundance within several inflammatory skin lesions, for example, psoriasis, contact sensitivity and allergic dermatitis.
Recent studies have revealed that CLA+ memory cells also express the chemokine receptor CCR10 and that cells expressing CCR10 are enriched in inflammatory skin lesions. One ligand for this receptor, CCL27, is also markedly up-regulated at these sites suggesting that this chemokine receptor may participate in mediating the tissue-specific trafficking of CLA+ memory T cells. Within the skin, expression of CCR10 has been reported on CLA+ T cells, melanocytes, fibroblasts, and microvascular endothelial cells. CCL27 expression has been shown to be tightly regulated with abundant expression in the epidermis, predominantly by keratinocytes.
There is evidence in both humans and in rodents that the CCR10-CCL27 interaction plays an important role in the trafficking of inflammatory T cell subsets to skin lesions. By histological analysis, it is clear that, in addition to the increase in epidermal expression of CCL27 observed in psoriatic and atopic dermatitis biopsies, there is also expanded expression of CCL27 into the dermal layer as well. Further, endothelial cells within the vasculature of these lesions also display CCL27, though they are negative for CCL27 message, suggesting that keratinocyte-derived CCL27 can be captured by endothelial cells and presented to circulating leukocytes. Accompanying these changes in the skin is a marked increase in the recruitment of lymphocytes that co-express CLA and CCR10. Consistent with the role of CCL27 in skin inflammation, IL-1 beta and TNF alpha treatment of cultured keratinocytes induces expression of CCL27.
Cutaneous application of nickel, in nickel-allergic humans, led to the up-regulated expression of CCL27 and the subsequent recruitment of CCR10+ lymphocytes. Thus, these studies provide temporal support for the role of CCL27 in attracting CCR10+ cells. Furthermore, in vivo proof of concept has been shown in wild-type mice where treatment with a function blocking antibody against CCL27 clearly diminished recruitment and swelling in both DNFB-induced and ovalbumin DTH models of dermatitis. These authors also demonstrated the ability of cutaneous injection of CCL27 to promote local lymphocyte trafficking and inflammation, thus providing proof of concept using both ligand and antibody in relevant animal models. Consistent with its ascribed in vivo role, CCL27 induces calcium flux in CCR10+ cells and mediates the selective chemotaxis of CLA+ CCR10+ lymphocytes in vitro.
Studies, such as those described above, suggest that antagonism of the interaction between CCR10 and its skin derived ligand CCL27 could therefore be of benefit in the treatment of inflammatory skin diseases by blocking the entry and activation of T cells within the skin. One indication for a CCR10 antagonist would be psoriasis. The rationale is based on histological studies of receptor/ligand expression in humans with psoriasis and proof of concept studies in animal models of skin inflammation. From analysis of normal and diseased skin samples, it is clear that the expression of CCR10 is highly regulated and restricted primarily to a subset of skin homing (CLA+) lymphocytes, dermal endothelial cells, and dermal fibroblasts. In addition, CCL27, a ligand for CCR10, is also expressed in keratinocytes. In normal skin, CCL27 is expressed by keratinocytes in the basal layers of the epidermis. However, in the skin of atopic dermatitis and psoriasis patients this ligand is up-regulated with expression extending to the suprabasal layers of the epidermis and histological staining also evident on the dermal microvasculature. The enhanced expression of CCL27 is accompanied by an increased presence of CCR10+ lymphocytes. Finally the proof of concept studies described above demonstrated that a function blocking antibody directed against CCL27 blocked trafficking of lymphocytes and swelling in two murine models of dermatitis.
Based on the pattern of expression for both CCR10 and CCL27 and the above proof of concept studies, CCR10 may also be a promising target for treatment of contact sensitivity and allergic dermatitis. It has been shown recently that CCL27 is increased in the sera of patients with systemic sclerosis and in the dermis of UV-induced cutaneous SLE (systemic lupus erythematosus) lesions. Therefore, systemic sclerosis and cutaneous SLE could also be additional indications. In addition, inflammation of the respiratory tract in a murine model of allergic asthma is associated with CCL28 and CCR10 expression suggesting that inhibition of CCR10 activity may also be useful in treatment of allergic asthma.
Antagonism of CCR10 may also be beneficial for the treatment of melanoma. In a mouse model of melanoma metastasis, it has been demonstrated that melanoma lines expressing CCR10 form tumors more readily than matched CCR10 deficient melanomas and that a blocking antibody against CCL27 can block the growth of these CCR10+ melanoma cells in vivo. These observations, coupled with the finding that many human melanomas express CCR10, provide the rationale for considering this as a further indication.